arXiv subjects

Marina Pivetta

Publications and source records attributed to Marina Pivetta.

3 recordsLinked to original sources

arXiv2026

Variable Charge State, Magnetic Excitations, and Kondo Effect of Sm/g/Ir(111)

Using low-temperature scanning tunneling microscopy we investigate the charge state, magnetic excitations, and Kondo features of individual Sm adatoms on graphene/Ir(111). Depending on the number and distance of their neighbors, Sm atoms can be in two discrete charge states. At certain distances, a reversible transition between these two states is induced by the electric field of the STM tip leading to concentric charge rings in the images. Only atoms in one of the two charge states exhibit magnetic excitations in d$I$/d$V$ spectra. Two such excitations are located at 35~meV and 54~meV and related to transitions from the $J = 1/2$ ground state doublet to the first crystal field split $J = 3/2$ multiplet. Together with the intra-atomic exchange excitations at higher energy, these observations indicate that Sm transfers one $6s$ electron to the substrate while it retains its gas-phase $4f$ filling. New for lanthanide adatoms, we observe a Kondo resonance. The Zeeman splitting of the Kondo peak reveals that Sm retains its large gas-phase $g$-factor. Comparison of d$I$/d$V$ spectra to cotunneling theory yields the crystal field acting on the $4f$ shell and, consequently, on the $J = 3/2$ quadruplet, confirms Sm$^+$ as the ground state, and identifies Sm$^{2+}$ as being energetically close, thereby rationalizing our observation of variable charge states.

cond-mat.mes-hall↗

arXiv2020

Orbital-resolved single atom magnetism measured with X-ray absorption spectroscopy

Lanthanide atoms and molecules are promising candidates for atomic data storage and quantum logic due to the long magnetic lifetime of their electron quantum states. Accessing these states through electrical transport requires the engineering of their electronic configuration down to the level of individual atomic orbitals. Here, we address the magnetism of surface-supported lanthanide atoms, clusters, and films with orbital selectivity using X-ray absorption spectroscopy and magnetic circular dichroism. We exploit the selection rules of electric dipole transitions to reveal the occupation and magnetism of the valence electrons of Gd and Ho deposited on MgO/Ag(100). Comparing our results with multiplet calculations and density functional theory, we identify a charge transfer mechanism that leaves the lanthanide species in an unconventional singly ionized configuration. Our approach allows determining the role of valence electrons on the quantum level structure of lanthanide-based nanostructures.

cond-mat.mes-hall↗

arXiv2005

Fluorescence and phosphorescence from individual C$_{60}$ molecules excited by local electron tunneling

Using the highly localized current of electrons tunneling through a double barrier Scanning Tunneling Microscope (STM) junction, we excite luminescence from a selected C$_{60}$ molecule in the surface layer of fullerene nanocrystals grown on an ultrathin NaCl film on Au(111). In the observed luminescence fluorescence and phosphorescence spectra, pure electronic as well as vibronically induced transitions of an individual C$_{60}$ molecule are identified, leading to unambiguous chemical recognition on the single-molecular scale.

cond-mat.other↗